9h22m02.6s, +50° 58′35″| NGC 2841 | |
|---|---|
AHubble Space Telescope image of NGC 2841
| |
| Observation data (J2000 epoch) | |
| Constellation | Ursa Major |
| Right ascension | 09h22m 02.655s[1] |
| Declination | +50° 58′ 35.32″[1] |
| Redshift | 0.002130[2] |
| Heliocentric radial velocity | 638 km/s[3] |
| Distance | 46.0 ± 4.9 Mly (14.1 ± 1.5 Mpc)[4][5] |
| Apparent magnitude (V) | 10.1[3] |
| Characteristics | |
| Type | SAa[2] |
| Mass | 7×1010 M☉[6] M☉ |
| Apparent size (V) | 8.1′ × 3.5′[6] |
| Notable features | Flocculent galaxy with LINER nucleus |
| Other designations | |
| UGC 4966, PGC 26512[3] | |
NGC 2841 is an unbarred spiral galaxy in the northern circumpolar constellationofUrsa Major. It was discovered on 9 March, 1788 by German-born astronomer William Herschel. J. L. E. Dreyer, the author of the New General Catalogue, described it as, "very bright, large, very much extended 151°, very suddenly much brighter middle equal to 10th magnitude star".[7] Initially thought to be about 30 million light-years distant, a 2001 Hubble Space Telescope survey of the galaxy's Cepheid variables determined its distance to be approximately 14.1 megaparsecs or 46 million light-years.[4] The optical size of the galaxy is 8.1′ × 3.5′.[6]
This is the prototype for the flocculent spiral galaxy,[5] a type of spiral galaxy whose arms are patchy and discontinuous.[8] The morphological class is SAa, indicating a spiral galaxy with no central bar and very tightly-wound arms. There is no grand design structure visible in the optical band, although some inner spiral arms can be seen in the near infrared.[5] It is inclined by an angle of 68° to the line of sight from the Earth, with the major axis aligned along a position angle of 148°.[5]
The properties of NGC 2841 are similar to those of the Andromeda Galaxy.[4] It is home to a large population of young blue stars, and a few H II regions.[9] The luminosity of the galaxy is 2×1010 L☉ and it has a combined mass of 7×1010 M☉.[6] Its disk of stars can be traced out to a radius of around 228 kly (70 kpc). This disk begins to warp at a radius of around 98 kly (30 kpc), suggesting the perturbing effect of in-falling matter from the surrounding medium.[5]
The rotational behavior of the galaxy suggests there is a massive nuclear bulge,[6] with a low-ionization nuclear emission-line region (LINER) at the core; a type of region that is characterized by spectral line emission from weakly ionized atoms.[10] A prominent molecular ring is orbiting at a radius of 7–20 kly (2–6 kpc), which is providing a star-forming region of gas and dust.[6] The nucleus appears decoupled and there is a counter-rotating element of stars and gas in the outer parts of the nucleus, suggesting a recent interaction with a smaller galaxy.[6]
Four supernovae have been observed in NGC 2841: SN 1912A (type Ia, mag. 13),[11] SN 1957A (type Ia, mag. 14),[12] SN 1972R (mag. 16),[13] and SN 1999by (type Ia, mag. 15).[14]
